1. Field of the Invention
The present invention relates to a light guide structure, and more particularly to a light guide having a light condensing effect.
2. Description of Prior Art
At present, many small electronic devices such as mobile phones, personal digital assistants, global positioning systems are necessary electronic products indispensable to our daily life. These electronic products generally come with a small keypad structure provided for users to input data or execute different functions of the electronic products.
The keypad structure of these electronic devices comes with a backlight source for providing a backlight effect for the keypad where there is insufficient light, and the light of the backlight source can penetrate through the surface of the push button to show a number, a figure or a pattern on the surface of the push button, and thus users will not press the wrong push button while operating the push button on the keypad.
In recent years, many keypad manufacturers try to reduce the overall thickness of the keypad structure, and two light emitting diodes 20 used for the backlight source are installed on both lateral sides of a light guide plate 10 (as shown in FIG. 10). If the light emitting diode 20 is lit, the light is guided along the lateral sides of the light guide plate 10 to evenly illuminate the whole light guide plate 10, and then the light is projected from the light guide plate 10 onto each push button of the keypad. If the light is passed through the surface of the push button, the number or figure on the surface of the push button will be illuminated and displayed for facilitating users to execute their operations.
After light is guided from a lateral side of the light guide plate 10 to another side, the brightness of the light becomes progressively weaker, so that an insufficient light transmission occurs at the surface of the corresponding push button on the other lateral side of the light guide plate 10 and results in an insufficient brightness for displaying the number or figure. To enhance the brightness of the light guide plate 10, a single light emitting diode with a large number of milliamperes (mA) such as 20 mA is used, and the total number of mA of the light emitting diode will be equal to 40 mA, and such arrangement will increase the power consumption and the cost of the electronic device.